Substrate treating method and substrate treating apparatus

ABSTRACT

The apparatus includes a chamber having a treating space for treating the substrate, a substrate support unit for supporting the substrate in the treating space, a gas supply unit for supplying gas into the treating space, and a plasma source for generating plasma from the gas supplied to the treating space, wherein the gas supply unit includes a shower head unit disposed in a top portion of the chamber so as to face away the substrate support unit, wherein a plurality of discharge holes are defined in the shower head unit, wherein the gas is discharged through the discharge holes, and a gas block for supplying the gas to the shower head unit, wherein the shower head unit has partitioned regions defined therein communicating with the discharge holes respectively, wherein the gas block supplies the gas to the partitioned regions at different flow rates.

CROSS-REFERENCE TO RELATED APPLICATIONS

A claim for priority under 35 U.S.C. § 119 is made to Korean PatentApplication No. 10-2019-0076764 filed on Jun. 27, 2019 in the KoreanIntellectual Property Office, the entire contents of which are herebyincorporated by reference.

BACKGROUND

Embodiments of the inventive concept described herein relates to asubstrate treating method and a substrate treating apparatus, and moreparticularly, to a substrate treating method and a substrate treatingapparatus for treating a substrate using gas.

In a process of manufacturing a semiconductor device, various processessuch as photographing, etching, thin-film deposition, ion implantation,and cleaning are performed. A substrate treating apparatus using gas isused for etching, thin-film deposition, ion implantation, and cleaningprocesses among the above processes.

In general, a gas treating process includes supplying process gas into achamber to treat a substrate using the process gas. A shower head havinga size similar to that of the substrate is placed above the substratesuch that the process gas is uniformly supplied onto an entire region ofthe substrate. The shower head has a plurality of discharge holesdefined in a surface thereof facing the substrate. Thus, a process gasis supplied from each discharge hole to the substrate to treat thesubstrate using the process gas.

In general, the discharge holes have the same shape and supply the gasat the same flow rate. However, during the process, a portion of theprocess gas reacts with the shower head to change a size of thedischarge hole. For example. The process gas may act as an etching gasto remove a film of the substrate, and the process gas may etch theshower head.

In particular, the discharge extends from an inner end to a dischargeend, and the discharge end is exposed to a space where the substrate istreated. Accordingly, as shown in FIG. 1, a discharge end 2 a is exposedto a larger amount of the etching gas than an inner end 2 b is exposed.Thus, as the process repeats, discharge end 2 a has a larger diameterthan that of the inner end 2 b.

As a result, the discharge holes discharge the process gas at differentflow rates, which causes uneven gas treatment. In particular, the gasfrom a central region of a shower head 2 may have a lower gas flow ratethan the gases from other regions thereof. In this case, as shown inFIG. 2, the process gas is exhausted from the central region but doesnot reach the substrate.

SUMMARY

Embodiments of the inventive concept provide an apparatus and a methodcapable of uniformly treating a substrate using a process gas.

Moreover, embodiments of the inventive concept provide an apparatus anda method in which a process gas is discharged at an uniform rate acrossregions.

The purposes of the inventive concept are not limited thereto. Otherpurposes as not mentioned will be clearly understood by those skilled inthe art from following descriptions.

According to an exemplary embodiment, an apparatus for treating asubstrate includes a chamber having a treating space for treating thesubstrate, a substrate support unit for supporting the substrate in thetreating space, a gas supply unit for supplying gas into the treatingspace, and a plasma source for generating plasma from the gas suppliedto the treating space, wherein the gas supply unit includes a showerhead unit disposed in a top portion of the chamber so as to face awaythe substrate support unit, wherein a plurality of discharge holes aredefined in the shower head unit, wherein the gas is discharged throughthe discharge holes, and a gas block for supplying the gas to the showerhead unit, wherein the shower head unit has partitioned regions definedtherein communicating with the discharge holes respectively, wherein thegas block supplies the gas to the partitioned regions at different flowrates.

The apparatus may further include a controller to control the gas block,wherein when viewed from above, the partitioned regions includes: afirst region containing a center, and a second region surrounding thefirst region, wherein the gas block includes a body having a first fluidchannel defined therein connected to the first region and a second fluidchannel defined therein connected to the second region, a first adjusterfor adjusting a flow rate of gas flowing in the first fluid channel tobe a first flow rate, and a second adjuster for adjusting a flow rate ofgas flowing in the second fluid channel to be a second flow rate,wherein the controller may control the first and second adjusters suchthat the first flow rate and the second flow rate are different fromeach other.

The controller may control the first and second adjusters such that thefirst flow rate is higher than the second flow rate.

The controller may control the first adjuster to increase the first flowrate as a number of processes to treat the substrate increases.

The controller may control the second adjuster to increase the secondflow rate as a number of processes to treat the substrate increases.

The controller may control the first and second adjusters to increasethe first and second flow rates respectively such that a flow rate ofgas to be supplied to a space between the shower head unit and thesubstrate support unit is constant.

According to an exemplary embodiment, a method for treating a substrateincludes discharging a process gas from first and second partitionedregions defined in the shower head unit toward a substrate, thereby totreat the substrate using the process gas, wherein first and second flowrates of the gas to be supplied to the first region and the secondregion respectively are different from each other.

When viewed from above, the first region may contain a center, and thesecond region may surround the first region, wherein the second flowrate is lower than the first flow rate.

The substrate may include first to N-th substrates (n is a naturalnumber larger than 2), wherein treating the substrate using the processgas includes treating the first to N-th substrates sequentially usingthe process gas, wherein the first flow rate during a process fortreating the N-th substrate is higher than the first flow rate during aprocess for treating the first substrate.

The process gas may include etching gas to etch the substrate.

BRIEF DESCRIPTION OF THE FIGURES

The above and other objects and features will become apparent from thefollowing description with reference to the following figures, whereinlike reference numerals refer to like parts throughout the variousfigures unless otherwise specified, and wherein:

FIG. 1 is a view showing a discharge hole of a conventional shower head;

FIG. 2 is a view showing flow of gas discharged from the shower head ofFIG. 1;

FIG. 3 is a cross-sectional view showing a substrate treating apparatusaccording to an embodiment of the inventive concept;

FIG. 4 is a plan view showing a baffle of FIG. 3;

FIG. 5 is a cut-out perspective view schematically showing a shower headunit of FIG. 3;

FIG. 6 is a plan view showing a distribution plate of FIG. 5;

FIG. 7 is an enlarged view showing a discharge hole in each region ofFIG. 5; and

FIG. 8 is a view showing flow of gas discharged from each discharge holein FIG. 7.

DETAILED DESCRIPTION

Hereinafter, embodiments of the inventive concept will be described inmore detail with reference to the accompanying drawings. The embodimentsof the inventive concept may be modified in various forms, and a scopeof the inventive concept should not be interpreted as being limited tofollowing embodiments. The embodiments are configured to more fullyconvey the inventive concept to those of ordinary skill in the art.Therefore, a shape of each of elements in the drawings is exaggerated toemphasize a clearer illustration.

In this embodiment, a substrate treating apparatus for etching asubstrate using plasma in a chamber will be described as one example.However, the inventive concept is not limited thereto. Any apparatusthat treats a substrate using gas discharged from a shower head unit maybe applied to various processes.

Hereinafter, the inventive concept will be described with reference toFIG. 3 to FIG. 8.

FIG. 3 is a cross-sectional view showing a substrate treating apparatusaccording to an embodiment of the inventive concept. Referring to FIG.3, a substrate treating apparatus 10 includes a chamber 100, a substratesupport unit 200, a plasma source 400, a baffle 500, a gas supply unit600, and a controller 900.

The chamber 100 provides a treating space in which a substrate W istreated. The chamber 100 has a circular cylinder shape. The chamber 100is made of metal material. For example, the chamber 100 may be made ofaluminum material. An opening 130 is formed in one side wall of thechamber 100. The opening 130 is embodied as an entrance 130 throughwhich the substrate W may be brought into the chamber and may be takenout from the chamber. The entrance 130 may be opened and closed by thedoor 140. An exhaust hole 150 is formed in a bottom surface of thechamber 100. The exhaust hole 150 is connected to a decompression member160 via an exhaust line. The decompression member 160 provides a vacuumpressure to the exhaust hole 150 via the exhaust line. By-productsgenerated during the process and plasma remaining in the chamber 100 aredischarged outside the chamber 100 using the vacuum pressure.

The substrate support unit 200 supports the substrate W in the treatingspace. The substrate support unit 200 may be embodied as anelectrostatic chuck 200 for supporting the substrate W using anelectrostatic force. Optionally, the substrate support unit 200 maysupport the substrate W in various schemes such as mechanical clamping.

The electrostatic chuck 200 includes a dielectric plate 210, a focusingring 250, and a base 230. The substrate W is placed directly on a topsurface of the dielectric plate 210. The dielectric plate 210 has a discshape. The dielectric plate 210 may have a radius smaller than that ofthe substrate W. An inner electrode 212 is installed inside thedielectric plate 210. A power source (not shown) is connected to theinner electrode 212, and power is applied from the power source (notshown) thereto. The inner electrode 212 provides an electrostatic forceusing an applied power (not shown) so that the substrate W is suctionedonto the dielectric plate 210. Inside the dielectric plate 210, a heater214 for heating the substrate W is installed. The heater 214 may belocated under the inner electrode 212. The heater 214 may be embodied asa coil in a spiral shape. For example, the dielectric plate 210 may bemade of a ceramic material.

The base 230 supports the dielectric plate 210 thereon. The base 230 islocated below the dielectric plate 210, and is fixedly coupled to thedielectric plate 210. A top surface of base 230 has a stepped shape suchthat a central region thereof is higher than an edge region thereof. Thebase 230 has an central region of the top surface having an areacorresponding to an area of a bottom surface of the dielectric plate210. A cooling fluid channel 232 is formed inside the base 230. Thecooling fluid channel 232 is embodied as a passage through which acooling fluid circulates. The cooling fluid channel 232 may have aspiral shape inside the base 230. The base is connected to ahigh-frequency power source 234 located outside the base. Thehigh-frequency power source 234 applies power to the base 230. The powerapplied to the base 230 guides plasma generated in the chamber 100 tomove toward the base 230. The base 230 may be made of a metal material.

The focusing ring 250 focuses the plasma onto the substrate W. Thefocusing ring 250 includes an inner ring 252 and an outer ring 254. Theinner ring 252 has an annular ring shape surrounding the dielectricplate 210. The inner ring 252 is located on an edge region of the base230. A top surface of the inner ring 252 is configured to have the samevertical level as that of a top surface of the dielectric plate 210. Atop surface of an inner portion of the inner ring 252 supports a bottomsurface of an edge region of the substrate W. For example, the innerring 252 may be made of a conductive material. The outer ring 254 has anannular ring shape surrounding the inner ring 252. The outer ring 254 islocated adjacent to the inner ring 252 on the edge region of the base230. A top surface of the outer ring 254 has a vertical level higherthan that of the top surface of the inner ring 252. The outer ring 254may be made of an insulating material.

The plasma source 400 excites the process gas in the chamber 100 into aplasma state. In one example, the plasma source 400 may be embodied as acapacitively coupled plasma (CCP) source. The plasma source 400 mayinclude an upper electrode and a lower electrode (not shown) inside thechamber 100. An upper electrode 420 and the lower electrode may bearranged vertically and may be parallel to each other in an interior ofthe chamber 100. A high-frequency power may be applied to one of theupper and lower electrodes, while the other electrode may be grounded.An electromagnetic field may be generated in a space between bothelectrodes, and thus the process gas supplied to this space may beexcited into a plasma state. In one example, the upper electrode 420 maybe disposed in a shower head 650, and the lower electrode may bedisposed in the base. The high-frequency power may be applied to thelower electrode, and the upper electrode 420 may be grounded.Alternatively, the high-frequency power may be applied to both the upperand lower electrodes. Thus, the electromagnetic field is generatedbetween the upper electrode 420 and the lower electrode. The generatedelectromagnetic field excites the process gas contained inside chamber100 into the plasma state.

The baffle 500 uniformly exhausts the plasma across the regions in thetreating space in a separate manner. FIG. 4 is a plan view showing thebaffle in FIG. 3. Referring to FIG. 4, the baffle 500 is located betweenan inner wall of the chamber 100 and a substrate support unit 400 in thetreating space. The baffle 500 has an annular ring shape. A plurality ofthrough-holes 502 are formed in the baffle 500. Each of thethrough-holes 502 may extend in the vertical direction. Thethrough-holes 502 are arranged along a circumferential direction of thebaffle 500. Each of the through-holes 502 has a slit shape extending ina radial direction of the baffle 500.

The gas supply unit 600 supplies the process gas into the treatingspace. The gas supply unit 600 includes a shower head unit 600 and a gasblock 800. The shower head unit 600 is positioned above the substrate Wlocated on the substrate support unit 400 and faces away the substrateW. The shower head unit 600 has a plurality of discharge holes 712defined in a bottom surface thereof facing the substrate W. The showerhead unit 600 is installed on an upper wall of the chamber 100. In oneexample, the shower head unit may be positioned so that a central axisthereof coincides with a central axis of the chamber 100. For example,the process gas may be etching gas.

The gas block 800 supplies the process gas to the shower head unit 600.The shower head unit 600 has a plurality of regions partitioned fromeach other defined in the shower head unit 600. These regions are incommunication with the discharge holes 712. The gas block 800 suppliesthe process gas to each of the partitioned regions. The gas block 800supplies the process gas to the regions at different flow rates.

Hereinafter, the shower head unit 600 will be described in more detail.FIG. 5 is a cut perspective view schematically showing the shower headunit in FIG. 3. FIG. 6 is a plan view showing the distribution plate inFIG. 5. Referring to FIG. 5 and FIG. 6, the shower head unit 600includes a discharge plate 710, a distribution plate 730, and anintroducing plate 770. The discharge plate 710, the distribution plate730, and the introducing plate 770 are sequentially and verticallyupwards stacked in this order.

The discharge plate 710 has a plate shape. For example, the dischargeplate 710 may have a disc shape. The discharge plate 710 has a bottomsurface exposed to the treating space. The plurality of discharge holes712 are formed in the discharge plate 710. Each discharge hole 712extends in the vertical direction. The process gas is supplied to thetreating space through the discharge holes 712. The discharge hole 712extends from a bottom surface to a top surface of the discharge plate710. The discharge holes 712 have the same diameter along a lengthdirection of the plate 710. For example, a portion of the discharge hole712 corresponding to a bottom surface of the discharge plate 710 isdefined as a discharge end 712 a, and a portion of the discharge hole712 corresponding to a top surface of the discharge plate 710 is definedas an inner end 712 b. The discharge end 712 a is exposed to the processgas more frequently than the inner end 712 b is. Thus, the former isetched by the gas at a larger amount than the latter is. Accordingly,the discharge end 712 a may have a larger diameter than that of theinner end 712 b.

The distribution plate 730 heats the process gas and distributes theheaded gas to the discharge holes respectively located in the regions.The distribution plate 730 is located above the discharge plate 710. Thedistribution plate 730 includes an upper plate 740, a partitioning plate738, and a heater 750. The upper plate 740 has a partial disc shapepartially similar to the discharge plate 710. The upper plate 740 havedifferent regions having different heights. A bottom surface of theupper plate 740 has an edge region having a vertical level differentfrom that of a central region thereof. The bottom surface of the upperplate 740 may have an edge region having a vertical level higher thanthat of the central region. Accordingly, the upper plate 740 may havethe bottom surface whose the edge region has a stepped shape. Thecentral region of the bottom surface of the upper plate 740 faces thedischarge plate 710 and has a size corresponding to the discharge plate710. A plurality of extended holes 744 are formed in a central region ofthe upper plate 740. The upper plate 740 is in contact with a topsurface of the discharge plate 710. The number of the extended holes 744is equal to the number of the discharge holes 712. The upper plate 740is positioned such that the extended holes 744 and the discharge holes712 coincide with each other when viewed from above. Each of theextended holes 744 is formed in a stepwise manner so that a width of abottom end thereof is smaller than that of a top end. Therefore, whenviewed laterally, a combination of each extended hole 744 and eachdischarge hole 712 constitutes a single elongate hole extending from atop of the upper plate 740 to a bottom of the discharge plate 710.

The partitioning plate 738 extends upward from a top surface of theupper plate. The partitioning plate 738 divides the top surface of theupper plate into a plurality of partition regions. The partitioningplate 738 is embodied as a plurality of concentric rings. Thepartitioned regions may include a first region 734, a second region 735,and a third region 736. The first region 734 is a region containing acenter, the second region 735 is a region surrounding the first region734, and the third region 736 is a region surrounding the second region735. Each region is embodied as a space defined by the upper plate, thepartitioning plate 738, and the introducing plate 770.

The heater 750 is located inside the upper plate 740. For example, theheater 750 may be embodied a heating wire. The heater 750 may beembodied as a coil in a spiral shape.

An introduction plate 770 supplies the process gas supplied from a gassupply line to each region of the distribution plate 730. Theintroducing plate 770 is stacked on a top face of the upper plate 740.The introducing plate 770 has a disc shape having a size correspondingto a size of the top surface of the upper plate 740. The introducingplate 770 and the upper plate 740 may be fastened to each other viabolts and may be in close contact with each other. A plurality ofintroduction lines are formed in the introduction plate. A plurality ofintroduction lines are embodied as independent lines, and correspond tothe regions of the distribution plate 730 respectively. The upperelectrode 420 is stacked on a top face of the introducing plate 770. Theupper electrode 420 may generate an electromagnetic field with the lowerelectrode.

A cooling member is disposed in the introduction plate 770. The coolingmember has a cooling fluid channel 790 formed inside the introducingplate 770. The cooling fluid channel 790 is embodied as a passagethrough which cooling water or cooling fluid flows. Cooling water orcooling fluid prevents the distribution plate 730 and the dischargeplate 710 from being heated to a temperature above a limit temperature.

The gas block 800 supplies the process gas to each region of thedistribution plate 730 and is installed on the shower head unit 600. Inthis embodiment, the gas block 800 is installed on the upper electrode420. The gas block 800 includes a body 820 and a plurality of adjusters.The body 820 has a fluid channel extending from an introduction end to aplurality of branching ends defined therein. The fluid channel mayextend from the introduction end, then branch from branch points andextend to the branching end. The adjusters are respectively installed inthe fluid channels branching from the branch points and extending to thebranching end. For example, a fluid channel connected to the firstregion 734 may be defined as a first fluid channel 822, and a fluidchannel connected to the second region 735 may be defined as a secondfluid channel 824, and a fluid channel connected to the third region 736may be defined as a third fluid channel 826. Each adjuster adjusts aflow rate of the process gas flowing in each fluid channel. Theadjusters may adjust the flow rate of the process gas so that the flowrates of the process gases to be supplied to the regions are differentfrom each other. For example, a first adjuster 832 is installed in thefirst fluid channel 822, a second adjuster 842 is installed in thesecond fluid channel 824, and a third adjuster 852 is installed in thethird fluid channel 826. For convenience of description, a flow rate ofthe process gas flowing in the fluid channel is defined as a supply flowrate. A flow rate of the process gas discharged from discharge hole 712is defined as discharge flow rate.

The controller 900 controls the adjusters 832, 842, and 852independently. The discharge holes 712 may have different sizes due todamage or deformation of the discharge holes 712. Thus, the dischargeholes 712 may have different flow rates. Thus, the controller 900controls the adjusters 832, 842, and 852 to compensate for thedifference between the discharge rates of the discharge holes 712 in theregions. In one example, the controller 900 may allow the supply flowrates of the process gases to be supplied to the different regions to bedifferent from each other so that the discharge flow rates of theprocess gases to be discharged from the discharge holes 712 may beuniform. The controller 900 may increase the supply flow rate of theprocess gas as the diameter of a corresponding discharge hole 712increases, thereby to compensate for decrease of the discharge flow rateoccurring when the diameter of the discharge hole 712 increases.

When the shower head unit 600 is set up in the chamber, the dischargeholes 712 have the same diameter. However, during the procedure oftreating multiple substrates W, the process gas is discharged hundredsto tens of thousands of times. Thus, the process gas etches thedischarge plate 710 during the discharging procedure. Moreover, whenviewed from above, a portion of the treating space facing the firstregion 734 has a higher plasma density than those of other portionsthereof. Accordingly, the discharge hole 712 connected to the firstregion 734 has a higher degree of damage than that of each of thedischarge holes 712 connected to the second region 735 and the thirdregion 736. As a cumulative number of process times increases, thedischarge hole 712 connected to the first region 734 has a largerdiameter than those of other discharge holes 712. The controller 900 maycontrol the adjusters to supply the process gas flowing in the firstfluid channel 822 at a flow rate that is greater than that of theprocess gas flowing in the second fluid channel 824. Thus, the dischargeflow rates from the discharge hole 712 corresponding to the first region734 and from another discharge hole 712 corresponding to another regionmay be uniform.

Hereinafter, a procedure for treating the substrate W using thesubstrate treating apparatus as described above will be described. Theshower head unit having the discharge holes 712 of the same diameterdefined therein is installed in the chamber. First substrate to N-thsubstrate are sequentially treated using the process gas. When treatingthe first substrate using the gas, the supply flow rates of the firstfluid channel 822, the second fluid channel 824, and the third fluidchannel 826 are equal to each other. The discharge holes 712 have thesame diameter, such that the process gas is discharged at a uniformdischarge flow rate between the regions. During treatment of multiplesubstrates W, the discharge plate 710 is etched by the process gas.Accordingly, each of the discharge holes 712 has a larger diameter thanwhen treating the first substrate. Therefore, when treating the N-thsubstrate, the supply flow rate of the gas to be supplied to each regionis greater than when treating the first substrate. Thus, the process gasto be discharged to the first substrate and the process gas to bedischarged to the N-th substrate may be discharged at the same dischargeflow rate.

Moreover, the discharge holes 712 have different amounts of etchingbased on positions thereof. For example, the discharge hole 712 locatedin the central region has a greater amount of etching than those ofother regions. This means that the central region of the treating spacehas a higher gas density than those of the other regions, so that thedischarge hole 712 of the central region may have a greater amount ofetching than those of the other regions. Accordingly, the discharge hole712 in the central region has a larger diameter than that of thedischarge hole 712 in another region. Therefore, the supply flow rate ofthe process gas to be supplied to the first region 734 may be controlledto be higher than the supply flow rate of the process gas to be suppliedto each of the other regions. Accordingly, the discharge rate of theprocess gas to be discharged from the discharge hole 712 in the centralregion may be equal to that of the process gas to be discharged from thedischarge hole 712 in each of the other regions.

According to an embodiment of the inventive concept, even when the sizesof the discharge holes corresponding to the different regions aredifferent from each other, compensating for the difference between theflow rates of the gases to be supplied to the discharge holes may allowthe discharge rates of the gas to be uniform between the differentregions.

The effect of the inventive concept is not limited to theabove-described effects. Effects not mentioned will be clearlyunderstood by those skilled in the art from the present specificationand the accompanying drawings.

While the inventive concept has been described with reference toexemplary embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the inventive concept. Therefore, it shouldbe understood that the above embodiments are not limiting, butillustrative.

1. An apparatus for treating a substrate, the apparatus comprising: achamber having a treating space for treating the substrate; a substratesupport unit for supporting the substrate in the treating space; a gassupply unit for supplying gas into the treating space; and a plasmasource for generating plasma from the gas supplied to the treatingspace, wherein the gas supply unit includes: a shower head unit disposedin a top portion of the chamber so as to face away the substrate supportunit, wherein a plurality of discharge holes are defined in the showerhead unit, wherein the gas is discharged through the discharge holes;and a gas block for supplying the gas to the shower head unit, whereinthe shower head unit has partitioned regions defined thereincommunicating with the discharge holes respectively, wherein the gasblock supplies the gas to the partitioned regions at different flowrates.
 2. The apparatus of claim 1, further comprising a controllerconfigured to control the gas block, wherein when viewed from above, thepartitioned regions includes: a first region containing a center; and asecond region surrounding the first region, wherein the gas blockincludes: a body having a first fluid channel defined therein connectedto the first region and a second fluid channel defined therein connectedto the second region; a first adjuster for adjusting a flow rate of gasflowing in the first fluid channel to be a first flow rate; and a secondadjuster for adjusting a flow rate of gas flowing in the second fluidchannel to be a second flow rate, wherein the controller is configuredto control the first and second adjusters such that the first flow rateand the second flow rate are different from each other.
 3. The apparatusof claim 2, wherein the controller is configured to control the firstand second adjusters such that the first flow rate is higher than thesecond flow rate.
 4. The apparatus of claim 2, wherein the controller isconfigured to control the first adjuster to increase the first flow rateas a number of processes to treat the substrate increases.
 5. Theapparatus of claim 4, wherein the controller is configured to controlthe second adjuster to increase the second flow rate as a number ofprocesses to treat the substrate increases.
 6. The apparatus of claim 5,wherein the controller is configured to control the first and secondadjusters to increase the first and second flow rates respectively suchthat a flow rate of gas to be supplied to a space between the showerhead unit and the substrate support unit is constant. 7.-10. (canceled)